// https://leetcode-cn.com/problems/combination-sum/
// 39. 组合总和

#include <iostream>
#include <vector>
#include <string>
#include <unordered_set>
#include <map>
#include <unordered_map>
#include <algorithm>
#include <queue>
#include <limits.h>

using namespace std;

// struct ListNode {
//     int val;
//     ListNode *next;
//     ListNode() : val(0), next(nullptr) {}
//     ListNode(int x) : val(x), next(nullptr) {}
//     ListNode(int x, ListNode *next) : val(x), next(next) {}
// };

// struct TreeNode {
//     int val;
//     TreeNode *left;
//     TreeNode *right;
//     TreeNode() : val(0), left(nullptr), right(nullptr) {}
//     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
//     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
// };



class Solution {
public:
    vector<vector<int>> combinationSum(vector<int>& candidates, int target) {
        backtrack(candidates, target, 0);
        return result;
    }
private:
    vector<vector<int>> result;
    vector<int> group;

    void backtrack(vector<int>& candidates, int target, int start_index) {
        if (target < 0) return;

        if (target == 0) {
            result.push_back(group);
            return;
        }

        for (int i = start_index; i < candidates.size(); i++) {
            group.push_back(candidates[i]);
            backtrack(candidates, target - candidates[i], i);
            group.pop_back();
        }
    }
};



int main() {
    Solution obj = Solution();
}